Everything in the cosmos is self-evident - it is what it is to anyone with eyes to see it - but not to us. We do not have such eyes.
The human mind is not only capable of deceit and self-deceit, it is rarely capable of anything else. Unlike the inherent truth of everything in the cosmos, everything we believe is flawed by our Midas touch, which sucks the truth out of our every idea and replaces it with what we want to believe or have. The philosopher Heraclitus was right to warn us about the things we want.
The same passions and ideologies that lead us to engage dishonestly with the honest world also lead us to misunderstand everything about it, to project our priorities upon it. Those interpretations and meanings we project do not directly change the real world. They change the picture of the world - the map - we carry around in our heads. They create inaccuracies in that map, flattering the things we like, insulting the things we don't, and generally omitting everything we fail to recognize.
The picture of the cosmos in our heads is the only one we really perceive most of the time, which is why human beings repeatedly do the wrong things - they would have been the right things to do if their picture of the world represented reality, but it doesn't.
So as bad as the problem of truth is for human beings when we just consider the ways in which the surface appearances of things can deceive, the problem reveals itself to be shockingly, confoundingly worse when we realize that we rarely perceive even the true appearances of things because we're too busy reacting to the imaginary appearances of things in our heads, the ones overlaid with years and decades of assumptions, desires, prejudices, and defense mechanisms.
Clearly put, if we were such fools as to treat the appearances of things as though they held the truth, we would still be vastly wiser than we are, because we are a step further removed from the truth than that, treating instead our mental pictures of the appearances of things as though they held the truth.
But the problem is far worse than that. Each of us holds our own picture of the world, with our own idiosyncratic prejudices standing between us and reality. It is not one labyrinth of assumptions we have to navigate to reach to the true appearances of things. It is six billion competing labyrinths.
Then it gets worse, because in any modern culture the political process takes us further from reality. As history shows repeatedly, compromising between those labyrinths suppresses the vestigial truths left in them, because the average human delusion - the things we can all agree on - is what is least likely to be true because it's most likely to be what we want. Instead of correcting for our labyrinths, we build a new one that takes as its bricks and mortar not even the appearance of the truth but instead our manifold delusions.
The idea that anything can be truly evident to us as a species is refuted by the human condition. The idea that any "truth" can or should be "self-evident" to humanity, that we do not even need to work for certain truths because it's obvious that they're true - that's trying to make a virtue out of a human defect so vast it is the very wailing abyss where our respect for the truth ought to be.
The most certain thing you can say about the sef-evidence of truths is that the actual truths of the cosmos are indeed inherently self-evident, but never to human beings. We are indeed special among animals in the profundity of our benightedness.